Detection and Mitigation of Factual Hallucinations in Large Language Models: A Comparative Review of the Timing and Effectiveness of External Retrieval, Post-hoc Verification, and Evaluation Methods

Bingchen Zhou

doi:10.54254/2755-2721/2026.TJ29621

Abstract

Large language models (LLMs) excel at reasoning and generation but remain susceptible to factual hallucinations. This survey categorizes recent progress around the timing of intervention: First, through retrieval augmentation and explicit reasoning during generation; second, through post-hoc verification and self-correction after generation. Regarding the former, this survey reviews IRCoT, SELF-RAG, ReAct, and Atlas, highlighting how combining retrieval with thought chaining can reduce multi-layer errors and improve answer grounding in knowledge-intensive question answering. Regarding the latter, this study examines RARR, Chain-of-Verification (CoVe), CRITIC, and Reflexion, which explore evidence, generate verification questions, or revise outputs through repeated criticism while minimizing stylistic bias. This work also summarizes detection and evaluation practices (e.g., SelfCheckGPT, FACTSCORE) that quantify attribution, support, and completeness. Across various approaches, this study analyzes effectiveness, computational cost, latency, and robustness to noisy retrieval, identifying failure modes such as retrieval dependency, ungrounded verification, and domain-shift gaps. This survey provides practical guidelines: for constrained question answering and multi-step reasoning, a combined retrieval-and-reasoning approach is most effective; whereas post-hoc validation is more suitable for long-form generation and reporting, and for citing external sources. Finally, this work proposes open problems: a unified cost-aware controller that can adjust intervention frequency; stronger evidence attribution; richer benchmarks beyond open-domain question answering; and a clearer trade-off between efficiency and realism for more reliable and scalable hallucination suppression.

Keywords: Large language models , Factual hallucinations , Retrieval enhancement , Verification and self-correction

Article Information

Received: 11 November 2025

Published: 19 November 2025

DOI: https://doi.org/10.54254/2755-2721/2026.TJ29621

Article Type: Research Article

Cite this article

Zhou,B. (2025). Detection and Mitigation of Factual Hallucinations in Large Language Models: A Comparative Review of the Timing and Effectiveness of External Retrieval, Post-hoc Verification, and Evaluation Methods. Applied and Computational Engineering,207,83-90.

Data availability

The datasets used and/or analyzed during the current study will be available from the authors upon reasonable request.

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About this Volume

Volume Title: ACE Vol.207

Part of Series: Applied and Computational Engineering

ISSN: 2755-2721 (Print) / 2755-273X (Online)

Copyright & License

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